Download Geological Past - Government of New Brunswick

New Brunswick’s
Geological Past
New Brunswick geology forms a rich
tapestry of rock types and landscapes. In
several areas of the province, the rocks are
quarried for commercial purposes or
contain valuable mineral deposits. Some
of the deposits are being mined today,
whereas others remain to be discovered.
But how and when did they form?
New Brunswick's geological past began
about 1 billion years ago when the world
was already 3.5 billion years old. The
continents as we know them did not exist.
Instead, there was a giant supercontinent
that broke into tectonic plates or protocontinents around 600 million years ago.
For several hundred million years, the
plates gradually migrated around the
globe, driven by intense heat from beneath
the earth’s crust. Their movement
resembled a slow geological ‘dance’ in
which the continents repeatedly drifted
apart and then collided with each other
over time.
As the plates separated, whole oceans
developed between them. Sediments were
eroded from the continents and filled huge
valleys beneath the expanding sea. As the
plates moved together and the oceans
closed, volcanoes erupted and mountains
formed at buckling plate margins. The
boundaries of plate separation altered with
each opening and closing, so that New
Brunswick-to-be became a montage of
varying rock types from different ages. The
oldest known rocks in New Brunswick
were deposited within warm shallow seas
during an early period of ocean opening,
and include the limestone currently
quarried near Saint John.
Contact information:
Les Fyffe, Director of
Geological Surveys
Department of Natural
Resources and Energy
P. O. Box 6000,
Fredericton, N. B.
CANADA, E3B 5H1
Tel. (506) 453-2206
[email protected]
As the ocean opened at 480-465 million
years ago, volcanic rocks were erupted
onto the sea floor. Sea water circulating
through these hot volcanic rocks were
expelled at geyser-like vents called black
smokers. Metal-rich, superhot water
emitted from these black smokers was
responsible for forming the rich base
metal deposits in the Bathurst area.
Around 420 – 400 million years ago, as a
result of the collision brought about by the
closure of the ocean, large volumes of
magma were generated deep within the
earth. The magmas mostly solidified into
massive bodies of granite, which intruded
the older rocks. These granites have been
quarried for dimension stone and
aggregate material, and contain significant
mineral deposits such as the Lake George
antimony mine and Mount Pleasant tintungsten mine.
The foregoing eons of violent geological
activity ended about 370 million years ago
with a relatively tranquil era that lasted
over 120 million years. During the
Carboniferous Period, New Brunswick lay
near the present-day equator, and a
shallow sea encroached upon the land. As
the ocean slowly evaporated in the heat, it
precipitated out gypsum, potash,
limestone and salt deposits, all of which
have been mined in the province.
The hot humid environment also
encouraged the widespread growth of
plants that later were buried and altered to
coal. Plant and animal remains became oil
shales, albertite and natural gas. During
the same era, massive volumes of
sediment eroded from the Appalachian
Mountains and were deposited in river
systems as sand, gravel and clay. They
became the sandstones, conglomerates
and shales that overlie much of the
province today, and have been quarried for
a variety of purposes.
The present Atlantic Ocean began to open
about 250 million years ago, and is still
widening today. As the plates split apart,
volcanic rocks called basalts filled the
fractures caused by rifting. Such rocks can
be seen in several locales, including Grand
Manan Island where they contain rare
minerals called zeolites that attract
collectors from across the continent.